Etching of high-reflecting thin-film assemblies using ion-beam-figuring techniques

Ion-beam-figuring techniques have been applied to fabricate high-power transmission gratings for use in photoacoustic spectroscopy. A thin-film assembly of SiO(2) and TiO(2) layers on an SiO(2) substrate provides a high-reflecting characteristic at a desired wavelength. With standard photolithographic techniques a grating pattern is developed on the surface of the assembly then ion etched with ion-beam-figuring techniques. These gratings exhibit an increased factor of 25 in acoustic signal levels when compared with previously used chemical-etched silicon gratings. This increase was obtained owing to higher transmission, less thermal distortion, and the ability to withstand higher incident power levels.